SU517424A1 - Method of multi-electrode automatic surfacing under flux - Google Patents

Description

a welding generator with electrodes connected to its clamps and a weldable product; in fig. 2 - oscillograms of electrical processes of multi-electrode cladding by the proposed method.

The generator (Fig. 1) has a winding 1 of independent excitation and a winding 2 of sequential excitation, the regulation of the current of the independent excitation is carried out by a rheostat 3. The direction of the magnetic fluxes of the windings are indicated by arrows L and 5. The external circuit of the generator includes an electrode system 4 and the weldable product 5.

In the oscillogram (Fig. 2), curve a shows the voltage changes at the electrodes during the deposition process; accordingly, curve b is the total current in the system of electrodes; curves в, г, д, е, ж - frequency of impulses, and current amplitude in electrodes; and a null line for measuring current and voltage amplitudes; K, - time marks with an interval of 20 m / s.

The joint operation of the generator circuit and the electrodes (Fig. 1) is carried out in the following order.

For a reliable start of the process, when the electrodes 4 and product 5 are cold, before starting surfacing using a rheostat 3, the generator idling voltage is set within 30-35 V. After the start of surfacing, due to the coordinated action of magnetic fluxes, shown by arrows A and B, for example electrodes increase to 40-45 V, therefore 2-3 seconds after the start of surfacing with a rheostat 3 or using a time relay (not shown in the scheme), the voltage on the electrodes decreases to 29-30 V, for thin electrodes, for example, 2 mm, - to 25-26 V. From now on pulse pulsing of the electrodes is established, and the surfacing process does not require any additional adjustments.

In the initial deposition period, the ends of the electrodes 6 are unevenly fused. During the pauses between the pulses, the discharge gaps are filled with slag, through which a small current (10-15 A) flows through the slag process. The released Joule heat is maintained in the slag and at the ends of the electrodes 4, which causes the formation of discharges without contact of the electrodes of the surface of the weld 5.

Due to the inequality of the length of the discharge gaps and their continuous shortening caused by the supply of electrodes to the product, an arc pulse arises in the medium of ionized slag on the electrode with the discharge gap being the shortest and most ionized. At the time of the arcing of the arc discharge, an instantaneous current jump occurs — a pulse that induces a counter-e in the windings of the generator. d. self-induction causing instantaneous voltage drops on brushes

generator to the limits of idling and respectively on the electrodes (Fig. 2, curve a). A voltage drop occurs only at the moment of the pulse, then at 5 steady-state current amplitude it quickly rises, which contributes to the burning of the arc discharge, during which a drop of liquid metal is formed on the electrode.

When a current pulse occurs, significant electrodynamic forces of the electromagnetic field arise, which form and drop a drop of liquid metal from the electrode into the surfacing bath. Since the pulses on the electrodes follow in time

15 with a high frequency (30-40 Hz) and their duration is small, a large drop does not accumulate on the electrode. The metal is transported in the form of small droplets, which contributes to the rapid transfer of thermal energy into the solid phase.

0 electrode metal and its accelerated melting. In pulsed processes, energy is used much more completely, so the productivity of the deposition process increases by 60-70% (against group

5 melting by long arc discharges).-1 Small-drop transfer of metal from single electrodes does not cause strong disturbances of the surface of the surfacing bath, which

0 contributes to the quality formation of the surface of the layer of the weld metal.

After separating a drop of liquid metal from an electrode, the length of its discharge gap increases, and the conductivity decreases.

5 At this time, there is an electrode in the system, in which the discharge gap is shorter and the conductivity is higher, and the next arc pulse arises in it. At the moment of the appearance of a pulse, the voltage drops, and the previously burning impulse with an extended gap goes out, then the process repeats on another electrode.

Thus, impulses arise and die away, one after another continuously, selectively

5 distributed in the electrode system. At the same time, the average effective current in the system approaches the average value of the pulse current in a single electrode, exceeding its value by the amount of the slag process current in the system.

Special current sources of sufficient power to power multi-electrode cladding that have low voltage.

5 idle and increasing external performance, the industry does not release. However, for this purpose, a SG-1000 type generator (in a PSM-100 converter) is easily converted, for which it is sufficient to switch this generator from self-excitation to independent (extraneous) excitation (Fig. 1). With independent excitation, the tough characteristic of the SG-1000 generator changes to increasing, and

The power of this generator allows surfacing in a single pass, 100-120 mm wide, when two SG-1000 generators are connected for parallel operation, respectively, up to 200-240 mm.

When surfacing low- and medium-carbon steels, it is recommended to use the known welding fluxes AN-60 and AN-348 fine granulation. For the deposition of alloyed high carbon alloys-flux type AN-28. The supply of electrodes is carried out at a constant (independent) speed using a well-known two-roll mechanism. The electrodes are arranged with a front across the direction of the cladding with intervals between the axes equal to 3.5 of the electrode diameter. The electrodes are connected to the positive pole of the generator.

Claims (1)

Invention Formula A multielectrode automatic submerged arc deposition method, in which the electrode system is powered from a single welding current source with an external static characteristic of increasing shape and no-load voltage corresponding to the arc voltage, characterized in that, in order to improve the performance, quality and stability of the deposition process, before the start of surfacing, increase the no-load voltage of the welding current source to the limit sufficient to ignite the arc, and then reduce the no-load voltage a limit equal to the voltage drop in the electrode regions of the arc.